Magnetic repulsion type of suspension

ABSTRACT

A magnetic suspension for a rotating meter disk includes two magnets facing each other axially with their poles disposed alike so that the lower fixed magnet repels the upper rotary magnet. Each magnet has two poles of the same face area spaced apart not over 3 mm.

United States Patent [191 Milligan Apr. 30, 1974 MAGNETIC REPULSION TYPEOF 2,699,385 1/1955 lndergand et al 308/10 SUSPENSION 2,713,523 7/ 1955Medicus 2,747,944 5/1956 Baermann... Inventor: James Mllllgan, West y e,2,810,867 10/1957 Gilbert 317/1575 A FOREIGN PATENTS OR APPLICATIONSAssigneel Duncan Electric Company, 1,017,871 10/1957 Germany 308/10 ITippecanoe County, Ind.

22 F] d: A 14 1961 Primary Examiner-D. F. Duggan 1 16 ug Attorney,Agent, or Firm-Darbo, Robertson and [21] App]. No.: 131,286 'vandenburgh52 us. 01. 308/10 [571 ABSTRACT [51] Int. Cl. F16c 39/06 A m gnet uspnsion for a rotating meter disk in- [58] Field of Search 324/155; 308/10lu w magn ts f cing e h ther axially with their poles disposed alike sothat the lower fixed mag- [56] References Cit d net repels the upperrotary magnet. Each magnet has UNITED STATES PATENTS two poles of thesame face area spaced apart not over 2,651,550 9 1953 Sharp 308/10 32,658,805 [1/1953 Mendelsohn 308/10 15 Claims, 9 Drawing Figuresmimanmso 1974 3807l8l3 sum 2 0F 2 SOURCE OF FLASH CURRENT .sounce OFFLASH CURRENT IN V TOR.

(fame; 71/. M' 7022 BY 9120, M @m MAGNETIC REPULSION TYPE OF SUSPENSIONVarious pieces of apparatus have shafts which must be rotatable with avery small amount of friction, often with a requirement of remainingstable for years. A common example is the watt-hour meter (the familiarelectric meter of the home). Another example is a gyroscope. In thepast, various structures have been devised for reducing the frictionaldrag upon a shaft of such a structure. One of these, especially suitablewhen the shaft is substantially vertical, is to suspend it magneticallyso that the weight of the rotor does not ride on a thrust bearing withits attendant frictional drag, and danger of increasing drag due to dirtor wear. Although such magnetic suspensions have been successfully used,they have been subject to recognized defects.

In casual theory, magnetic suspension or support would seem to be idealfor reducing the frictional drag of the shaft supports. Upon morecareful examination, the theory has drawbacks. One is lack of lateralstability. If the rotor moves slightly off center there results amagnetic side thrust. This necessitates a centering bearing, which inturn reintroduces rotational drag on the shaft, wear problems, etc.Also, past magnetic suspensions have been too delicate or soft. A changein positioning can change the application of forces to the meter disk,affecting the accuracy of meter operation. In afsoft suspension, aminute change of magnetic strength produces a relatively great change ofpositioning. Also, in actual practice, there have been other faults,such as sensitivity to temperature changes and to external magnetfields. Also, if the magnetic fields from the two coacting polefacesboth have any unevenness in the strength about the axes, this will actto produce unwanted locking forces, causing the shaft to seek aparticular angular position and resisting the start of rotation.

An object of the present invention is to provide a structure forelectric meters or the like which will ameliorate the problemsencountered with prior art devices and methods. Through the use of theinvention, the

shaft is stably supported and the decentering side thrust introduced bymagneticv fields of the support, when other forces cause minordecentering, is relatively low. As a result, the'extent to which thecentering bearings must hold the shaft bearing is lessened, with acorresponding reduction of wear and frictional drag in the shaftbearings. In fact, the support by magnetic repulsion with centering alsoby magnetic repulsion, in accordance with one form of my invention, isdesigned to resist such side-shifting of the shaft as may be introducedby other factors. Also, as a resultof the design,

and of the highly stable nature of the magnetic mate- DESIGNATION or,FIGURES FIG. 1 is an elevational sectional view' of a portion of anelectric watt-hour meter embodying'my invention;

FIG. 2 is mainly a face view of one magnet, being also a section asviewed at line 2-2 of FIG. 1;

FIGS. 3 and 4 are vertical sectional views of modified construction;

FIG. 5 is a sectional view of a fixture for magnetizing theshaft-mounted magnet of FIG. 1;

FIG. 6 is a vertical sectional view of alternative apparatus formagnetizing the magnets of FIGS. 1 and 3;

FIG. 7 is a horizontal sectional view taken along the line 7-7 of FIG.5.

FIG. 8 is a sectional view of apparatus for magnetizing the shaft magnetof FIG. 4.

FIG. 9 is a sectional view of an apparatus for magnetizing the ringmagnet of FIG. 4.

GENERAL DESCRIPTION Although the foregoing disclosure offered for publicdissemination is detailed to insure adequacy and so aid understanding,this is not intended to prejudice that purpose of a patent which is tocover each new inventive concept therein, no matter how others may laterdisguise it by variations in form or additions or further improvements.The following claims are intended as the chief aim toward this purpose,as it is these that meet the requirement of pointing out the parts,improvements, or combinations in which the inventive concepts are found.I Referring to FIGS. 1 and 2, there is illustrated a portion of anelectric watt-hour meter having a frame generally l0 and a vertical,rotating, shaft generally 11,

carrying a disk 11. The associated elements of the 4 meter such asdriving and retarding magnets are well known but are not shown. Theirstructureand relation ship to the illustrated device-will be understoodby Magnets 30 and 35 are substantially identical. In accordancewith thepresent invention their four permanent magnet pole faces all faceaxially, are close together, and of the same area, and like poles aredirectly opposite one another. Thus the outer pole faces 38 and 41(having the same polarity) are of the same area as the inner pole faces39 and 42, and the grooves or spaces 40 and 43 each between the two polefaces of one magnet, are quite narrow, in fact narrower in theillustrated form than either pole face. This arrangement, with propermagnetization to support the rotation element with the illustrated gapbetween magnets 30 and 35 (about 0.05") provides a very stiffsuspension, and one in which the magnetic side thrust resulting fromminute displacements is very small. During normal operation, pin 19 andgraphite ring 25 (having a running fit with pin 19) confine the lateralmovement of magnet 30 to such minute lateral displacements that magneticside thrust is extremely low.

DETAILED DESCRIPTION Frame (only outstanding bosses of which are shown)carries an upper mounting stud 12 and a lower mounting stud 13. Each ofthe studs are circular in a transverse cross-section. They are receivedin suitable openings in the frame bosses l0 and held in place by capscrews 14. Stud 12 has an axial bore or cavity 15 of cylindricalconfiguration with a small rod or centering pin 16 extending along theaxis of the bore. Pin 16 is held in place by a die-cast plug 17.Similarly stud 13 has a bore or cavity 18 and a rod or centering pin 19along the axis thereof which rod is held in place by plug 20. Pins 16and 19 are accurately centered by virtue of being held centered whileplugs 17 and 20 are die-cast.

At each end of shaft 11 are cavities 22 and 23 respectively. Cavities 22and 23 are cylindrical in shape with their cylindrical axes coincidingwith the axis of shaft 11. Secured in one end of shaft 11 at the mouthof cavity 22 is a graphite bearing 24 having the opening aligned withthe axis of shaft 11, in which opening pin 16 is journaled. Acorresponding bearing 25 is secured to the opposite end of shaft 11 atthe mouth of cavity 23 Near the lower end of shaft 11 is a knurledsection 27 these cooperating to ensure dependable positioning of magnet30. While rotor magnet is held accurately centered on the shaft 11,binding metal 29' is die-cast in place. Alternatively (as in FIG. 3) themagent 30 may be cemented to a collar 29 with which centering is ensuredby interfitting parts, and which snugly fits the shaft and is tightenedthereon by setscrews.

Lower magnet is bound to stud 13 by die-cast metal 36, which may beapplied at the same time as plug 20.

Magnets 30 and 35 are identical. Magnet 35 includes an outer annularpole face 38 and an inner annular pole face 39. As illustrated, the twopole faces are separated by a groove 40. Likewise magnet 30 has an outerannular pole face 41 and an inner annular pole face 42 separated by agroove 43. The grooves and 43 are valuable, but not always essential. Itwill be noted in FIGS. 1 and 2 that pole faces 39 and 42 are wider thanpole faces 38 and 41. This is done so that the area of pole faces 39 and42 is approximately equal to the area of pole faces 38 and 41,respectively.

although best results are attained with approximate equality in area,perfection is not essential. However, any departure from area equalityis believed detrimental or wasteful. With more than somewhere around a40 percent difference in area between the outer pole faces and therespective inner pole faces, the added increments of metal of the largerpole will be functioning mainly in the inferior manner of a magnethaving only one of its poles in a repelling position.

Magnets 30 and 35 are magnetized so that the outer pole faces 41 and 38are of the same polarity and the inner pole faces 42 and 39 are both ofthe opposite polarity. In the illustrated embodiment the former aredesignated north poles while the latter are designated south poles.However, the polarity of both magnets could be reversed withoutsignificance depending upon the choice of the manufacturer. The use ofthe designations N and S in the drawing is merely to illustrate therelative polarity of the two pole faces; It is intended that the magnets30 and 35 have the same relative strength at all angles of rotationabout the axis of shaft 11. Thus the magnetic field about either one ofthe magnets is roughly that of a semi-toroid, with the plane of polefaces 41 and 42, for example, approximately bisecting the toroid, andbeing normal to the axis about which the toroid was formed. The pins 16and 19 which have been used are 0.019 inches in diameter. Because oftheir small size, zero or very small bearing load, and their beingjournaled in the graphite bearings 24 and 25, the frictional drag to therotation of shaft 11 is extremely small. During normal operation, thesepins resist any side thrust so that lateral shifting is extremely small.However, the structure is adequately protected in another way againstshock damage, as in shipment. Thus with the ends of shaft 11 received incavities 15 and 18, the shaft is thereby restrained against excessivelateral movement.

There is also protection against excessive axial displacement, whichwould otherwise be likely to occur in shipment. Thus pins 16 and 19 havesuitably small clearance, such as 0.010 inch to 0.015 inch, with theends of cavities 22 and 23. The latter may be formed by an inserted endstop bearing to allay fears of purchasers who know such end stops havebeen needed heretofore and may not at first have confidence in theexceptional degree of insensitivity to temperature changes hereachieved.

MAGNETIZING FIXTURE AND METHOD A fixture of magnetizing magnet 30 isillustrated in FIG. 5. It includes a frame generally 48 having an upperarm 49 and a base arm 50. An electro-magnet, generally 51, is mounted onbase arm 50. It includes a core 52 of soft magnetic material, the upperportion of which is annular in shape and defines annular pole face 53. Acasing 54 of soft magnetic material surrounds core 52 and defines anannular pole face 55. Pole faces 53 and 55 lie in a common plane and areseparated by a gap 56. The configuration of poles faces 55 and 53corresponds to the configuration of pole faces 41 and 42, respectively.Between core 52 and casing 54 in gap 56, (in the illustrated form) arethe windings of a coil 57 energized through a pair of wires 58. Theprojecting portion of shaft 1 1, immediately below pole face 42 fitssnugly into bore 59 of core 52 to center magnet faces 41 and 42 with thecorresponding faces 53 and 55 of the magnetizer.

It may be noted in this connection that the provision of grooves 40, 43is quite desirable in reducing the need for extremely precise centeringof the magnet pole faces on the pole faces of the magnetizer. It hasbeen found tolerable, with grooves 40 and 43 provided, to have the bore59 of a diameter 0.002 inch larger than the diameter of the interfittingportion of shaft 11. The limit has not been determined.

It is'also important that the windings of coil 57 extend quite close tothe plane of the magnetizer pole faces 53 and 55. Likewise the coilshould be concentrated very close to this area so that a largeproportion of the total ampere-turns will be in this area. It has beenfound possible to saturate the permanent magnets by using 1 1,000 to12,000 ampere turns in a coil extending from 0.005 inch to 0.150 inchfrom the plane of the faces. The turns of the coil should be firmlybound together, as by high temperature shellac also used for coating thewire for insulation.

With these various contributing factors, it has been found that magnetscan be produced of exceptionally high magnetic uniformity about the axisand with very nearly the maximum pole face strength 'of which a givenmagnet is capable. By pole faces is of course meant the faces at theends of that portion of the main magnetizing flux path lying within thepermanent magnet. In the case of magnet 30 these would obviously befaces 41 and 42 since they are in contact with the iron of themagnetizing unit. To distinguish these faces even more clearly fromfaces adjacent to them, where some leakage flux may escape, each of thefaces such as faces 41 and 42 can be designated a face of greatestconcentration of flux of that faces polarity or a face containing apolarity center.

STABILIZING MAGNETIC KNOCK-DOWN As is well known in regard to magnets ingeneral, after magnetization they should be subjected to a partialknock-down or demagnetization for stabilization purposes. This may beaccomplished in the case of the illustrated magnets in conventionalmanner as by insertion in an alternating field of constant strength andremoval therefrom.

Preferably wires 58 are connected to a source of flash current, e.g., acurrent of high intensity and short time duration. Such devices are wellknown in the art, and their current may be derived from condenserdischarge. The magnet to be energized, for example magnet 30, is placedin position in the electromagnet. A flash of heavy magnetizing currentis passed through coil 57 to magnetize the magnet to saturization.Thereafter, is stabilization is to occur on the same fixture, ademagnetizing current, which may be of reverse polarity, or oscillatory,of much less strength is passed through coil 57 to partiallydemagnetize-and stabilize the magnet. The residual magnetism of the twomagnets should be such as to support the desired weight with the desiredaxial distance between the corresponding faces e.g., faces 38 and 41, ofthe magnets when in use. In a particular specific embodiment thestrengths of the magnetic fields (and'of the demagnetizing current)required to achieve this spacing fairly closely can be readilydetermined empirically. Also, a special demagnetizing setup can beprovided to give a final increment of demagnetization, progressivelyincreasing the strength of successive spaced impulses until the exactdesired residual flux value is attained.

DEMAGNETIZATION WITH COMPENSATION The plane defined by the pole faces 38and 39 and that of pole faces 41 and 42 should be parallel to each otherand normal to the axis of shaft 11. In order to obtain the advantage ofless expensive manufacturing operations, some minute errors may beencountered. To minimize their effect, the following novel method formagnetizing and stabilizing magnet 30 can be employed.

Referring to FIG. 5 there is on arm 49 a plug 63 carrying a pin 64 whichis receivable in bearing 24 (FIG. 1) of shaft 11. Plug 63 is mounted inarm 49 so as to be vertically movable with respect to the arm. Pin 64and bore 59 are positioned so that their axes are coincident and veryaccurately normal to the plane defined by pole faces 53 and 55. In otherwords, the faces 53 and 55 are accurately formed as surfaces ofrevolution about the axis of pin 64 and bore 59. When magnet 30 andshaft 11 are first inserted into the fixture, plug 63 is raised so thatpin 64 does not enter the bearing in the top end of shaft 11. If theaxis of shaft 11 is not normal to the plane of pole faces 41 and 42,shaft 11 will be cocked off to one side as illustrated in dotted linesat 11". The magnet 30 will assume a position at which pole faces 41 and42 are in full face-to-face contact with pole faces 55 and 53. Theinitial magnetizing current is not passed through coil 57. After theinitial magnetizing of the magnet, shaft 11 is moved to a position atwhich pin 64 will enter the bearing in the top of the shaft. Inproduction, a quicker or more automatic device will probably be providedfor centering the shaft on its proper axis. In any event, the shaft 11is now held in the position illustrated in full lines in FIG. 5. Whilethe movement of shaft 11" to achieve this repositioning may be verysmall, if enough to be significant it will result in some loss of theface-to-face contact between the pole faces of the magnetizing magnet 51and the pole faces of the magnet 30. With the shaft 11 held in the fullline position, except that magnet 30 rests on magnet 51 as indicated bythe arrow, the demagnetizing current now is passed through coil 57. Theareas of magnet 30 fully in contact with the poles of electro-magnet 51will be de-magnetized the greatest amount. To the extent that there isan air gap between other portions of the pole 41 and 42 with respect tothe pole faces 55 and 53, respectively, a lesser amount ofde-magnetization will occur. The larger the gap, the smaller will be theamount of demagnetizing of that portion of magnet 30. Thus when theshaft with its magnet is mounted as illustrated in FIG. 1, to the extentthat there is a cocking of magnet 30 on shaft 11 with one side of magnet30 being closer to magnet 35 than is the opposite side of magnet 30,that one side of magnet 30 (the close side) will have a smaller residualmagnetism. The greater residual magnetism at the area of greatestspacing will tend to compensate for this greater spacing, and nearequality of magnetic field along a perpendicular plane results. Althoughthis compensating demagnetization is available if needed, presentexperience indicates that sufficiently accurate mounting of magnets 30and 35 can be achieved in production so that it will not be required.

MAGNETIZER FOR SHAFTLESS MAGNETS In FIG. 5 magnet 30 was centered byinterfitting of its shaft 11 with bore 59.

FIG. 6 shows a construction suitable for magnetizing magnets which arenot mounted on shafts. The construction of the electromagnet portion issimilar to that of FIG. 5, except that instead of having a bore 59 intowhich a shaft extends it is provided with a centering dowel 65 whichsnuggly fits into the bore or central aperture of the magnet to bemagnetized.

AIR-CLEANING OF MAGNETIZERS Preferably the magnetic cores 52 areprovided with slots 66 along their cylindrical faces, these slotsextending axially as seen best in FIGS. 5 and 6. The coil lead wires mayextend through one such slot. As seen in FIG. 7 there may be severalsuch slots spaced around the core 52. Preferably these slots communicatewith a hose 66' for supplying compressed air. This air will help keepthe pole faces of the magnetizer clean by blowing past the outside ofcoil 57 which is tightly mounted on core 52 but has a slight clearancewith shell 54.

MAGNETIC SUSPENSION WITH REPULSION CENTERING FIG. 4 illustrates thelower portion of a shaft 67 generally corresponding to shaft 11. Theupper end of shaft 67 (not shown) might be mounted in a bearingstructure corresponding to the upper mounting of shaft 11. Projectingfrom the bottom of shaft 67 is a pin 68 which may be quite stiff. It isshorter and may be of larger diameter than pins 16 and 19. Pin 68extends into a cavity 69 in a support block 70. Support block 70 wouldbe mounted on a suitable frame such as frame of FIG. 1.

Above cavity 69 is an enlarged cavity 71 at the bottom of which isseated a graphite bearing 72. Bearing 72 has an axial opening 73 toreceive pin 68 quite loosely. Surrounding the botton end of shaft 67 isa support magnet 74 which may be identical to magnet of FIG. 1. Magnet74 has an outer annular pole face 75 and an inner annular pole face 76,corresponding to pole faces 38 and 39, respectively. The two pole faces75 and 76 may be separated by a groove 77.

Rotor magnet 82 is secured about a knurled section 80 of shaft 67 bymetal 81 die cast in situ. Magnet body 82 is cylindrical in shape. Itsbottom plane is provided with an outer annular pole face 83 and an innerannular pole face 84 which may be separated by a groove 85. The shapeand size of pole faces 83 and 84 correspond to those of pole faces 75and 76.

About the periphery of magnet body 82 adjacent the upper end thereof area pair of circumferential pole faces 87 and 88, which may be separatedby a groove 89. An annular magnet 90 has a pair of inner circumferentialpole faces 91 and 92 separated by a groove 93.

Pole faces 87 and 91 are of one polarity while pole faces 88 and 92 areof the opposite polarity. Thus the magnetic field between the uppermagnet of body 82 and the ring magnet 90 is such that these magnets actto repel each other and will serve to center shaft 67 to coincide withthe vertical axis of pole faces 91 and 92. Pole faces 83 and 75 also areof one polarity, with pole faces 76 and 84 being of the oppositepolarity. Thus the bottom magnetic portion of magnet body 82 will besupported by the repelling magnetic force between that magnet body andmagnet 74. If the forces applied to the rotating element of whichspindle 67 is a partare fairly light or well balanced as to lateralforces on spindle 67, pin 68 will presumably never touch bearing 72during normal operation, and ordinary friction will be zero.

Similar results are expected from a single pair of nested magnets withfaces of conical shape. Thus each magnet is to have both of its faceslying in a surface of revolution about the axis which would be generatedby a line oblique to the axis. The groove between the poles of onemagnet should be displaced from the other along a cone perpendicular tothe cones of the faces. The outer magnet may have its inner faceextended to the same internal diameter as the opposing inner face, andits outer face extended to the horizontal plane of the outer diameter ofthe opposing outer pole.

Stator magnet 74 may be magnetized on an electromagnet such as thatillustrated in FIG. 5. FIGS. 8 and 9 respectively illustrate thefixtures for magnetizing magnet body 82 and ring magnet 90. Referring toFIG. 8, there is an annular core 95 of soft magnetic material having aslot therein to receive the electrical windings 96. At the same time theslot holding winding 96 defines a pair of circumferential pole faces 97and 98. A pair of annular rings 99 and 100 are positioned at oppositesides of core 95. The rings 99 and 100 are made of anelectro-conductive, non-magnetic, material such as copper.

The bottom face of magnet body 82 is magnetized by an electro-magnetwhich includes a core 102 having a slot in the upper face thereof toreceive winding 103. The slot receiving winding 103 together with theaxial opening 104 define annular pole faces 105 and 106 in juxtapositionto pole faces 83 and 84, respectively. Windings or coils 96 and 103 aresuitably connected to a source of flash current 107 such as that used toenergize coil 57 of the embodiment of FIG. 5. As in the embodiment ofFIG. 5, coils 96 and 103 are first energized by a relatively largeimpulse current of one polarity to magnetize magnet body 82 tosaturation. Thereafter a smaller impulse current of reverse polarity maybe passed through coils 96 and 103 to partially demagnetize the magnetbody. Coils 96 and 103 have been shown connected in series to indicatethat they are energized exactly in unison, so that neither willadversely affect the magnet the other magnetizes.

FIG. 9 shows the fixture for magnetizing magnet 90. A generallycylindrical core 109 has a slot therein to receive a winding 110. Theslot within which winding 1 10 is positioned defines a pair ofperipheral pole faces 111 and 112 generally corresponding to pole faces91 and 92 of magnet 90. A pair of cylindrical copper disks 103 and 104are positioned at opposite sides of core 109. Winding is connected tothe source of flash current 107. Initially it is energized by arelatively high current to saturate magnet 90. Thereafter it may beenergized by a somewhat lower current of opposite polarity to partiallydemagnetize magnet 90.

MAGNETIC CONSIDERATIONS To achieve the objects of my invention to bestadvantage it is important as has been noted that the width of grooves 40and 43 (as measured along a radial line) be quite small. The correctdimension for optimum results may vary, but it now appears that for safeachievement of these results the width of the gap 40, 43 should not bein excess of 3 mm, and it is believed that size would be inferior to thedimensions given below. Magnets 30 and 35 as now most thoroughly testedhave an overall diameter 0.564 inch and a bore diameter 0.156 inch, thewidth of groove 40 and 43 as measured along a radius is 0.043 inch. Poleface 39 has a radial dimension of 0.107 inch and pole face 38 has aradial dimension of 0.054. The magnets as measured along the axis ofshaft 11 may be 0.187 inch thick. The magnets may be made of one of thematerials well known to the art for forming high coercive permanentmagnets, such as one of the alloys sold under the tradename ALNICO. Avery high coercive material (at least 650 oersteds) should be used.Present preference is a molded composition of Alnico VII powder bound bya stable, thermosetting resin with a high heatdistortion temperature.Although the magnetized suspension of FIG. 4 has not yet beenconstructed, the smallness of magnetic side thrust encountered with theFIG. 1 type of suspension suggests that the FIG. 4 type may achievecomplete magnetic stability, even though that has seemed impossibleheretofore. At least, it will apparently achieve a condition of minimummagnetic sidethrust caused by minute eccentricity, and if this is all itachieves it should have the same type of centering pin as in FIG. 1.Grooves 89 and 93 should also be not over 3 mm in width (axialdimension) and preferably as small as practical, e. g., 0.04 inch.

The FIG. 1 form of the invention has been found exceedingly satisfactoryfor supporting 16 gram rotating elements, such as single phase meterrotors. On 32 gram elements (2 discs) greater magnetic side thrust isdeveloped by minute eccentric displacement, but it is still well withintolerable range, and the suspension is also satisfactory for thisheavier rotor. In fact this is the planned first commercial use.

Maintaining a small overall diameter for the magnets is important.Partly this is desirable for reasons of economy and compactness. Inaddition it shortens the torque arm of any force resultingfrom lack ofperfection in uniformity, thereby making such nonuniformity lessobjectionable than if it has a longertorque arm, or long leverage. Whenpossible the external diameter of the magnets should be kept at least assmall as threefourths inch. Where greater lifting force is required itwould be better to use'more pairs of magnets axially separated than touse one pair of magnets of larger diameter.

The outside diameter is kept at a minimum by having both pole faces ofone magnet of. the same area, and by keeping the separating groove smallas measured along a radius; both the factors being desirable for otherreasons also. By a resin of high heat distortion temperature is meantone which will withstand at least 250F without significant distortion bya moderate applied force. For example, five pounds applied through al/16 inch diameter ball should not leave a depression over 0.010 inch.

It is important that the stabilizing demagnetization be to a degree suchthat when the magnets are moved into the closest proximity permitted bythe physical dimensions of the parts, they will have no furtherpermanent demagnetizing effect. At present, a demagnetizing field ofabout 700 oersteds is used, and even face to face contact of the magnetswould have no further effect al though such contact is prevented.Demagnetization will also determine the length of the axial gap betweenmagnets when a given load is supported; At present an axial gap of about0.050 inch is used with a 35 gram total rotor weight (including therotor magnet). About 0.060 inch to 0.065 inch is planned for an 18 gramrotor, using smaller magnets. It will be observed that these axial gapsare longer than the width of the groove separating the magnet faces, bya substantial percentage. A gap slightly shorter than the groove widthhas also been used, but relative side thrust was increasing and muchless than this should apparently be avoided. In other words, axial gapshould be at least of the order of approximately equal to the groovewidth (or separation of the pole faces, if no groove).

Although mention has been made as to each magnet that the separation ofits magnetic poles should not be over 3 mm, it is believed that in fact,it should be as little as is practicable. Making it smaller than about0.04

Cobalt 24 Nickel I 8 Aluminum 8 k Titanium 5 Copper 3 V4 Iron remainderPRECISION DIE-CASTING It is, of course, extremely important that theplane of pole faces 38 and 39 he perpendicular to the axis of holder 13.Features illustrated in FIG. 1 facilitate achieving this in production.

One of the important features is the provision of a deformable annularrib 120 close to the cavity 18 of body 13. In the course of die-casting,the die which engages the pole faces 38 and 39, and which also fitswithin the central bore of magnet 35 for centering this magnet, ispressed with great force, such as a hundred pounds, toward the portionof the die which holds body 13 accurately centered therein. This forceis enough to upset or deform rib 120, the body 13 being of aluminum.Thus, if there is any minute irregularity which causes uneven spacingbetween magnet 35 and body 13 the annular rib 120 will be deformed toaccommodate itself to this irregularity. While the parts are thusheld inproperrelationship the die-casting metal will be in jected. The rib 120serves to seal the flowing metal from penetrating into the cavity 18 inthe vicinity which will later be occupied by the shaft 11.

In order for the die-cast portion 36 to be formed by the same injectionas the plug 20, bore 121 is provided transversely through the body 13.Thus the metal can flow from one source to all of the points shown. Ofcourse the die member which holds magnet 35 is provided with anextension which forms the inner contour of the die-cast metalconstituting the bottom portion of cavity 18.

- 6 inch appears to be difficult, however, 1n view of the need to use alarge number of ampere turns adjacent to the plane of the pole faces ofthe magnet being magne- CONCLUSION According to this invention anexceedingly stiff magnetic suspension is provided, without excessiveside thrust upon minute lateral displacement. In addition, tests haveshown that it has amazingly low sensitivity to temperature changes. Thissuspension has been used with a 32 gram rotor which moves axially onlyabout 0.003 inch or less with a temperature variation from minus 40C toplus C. This, of course, is far beyond the range to which watt-hourmeters are likely to be subjected. For comparison with one of the bestprior magnetic suspensions it may be noted that with the sametemperature variation a vertical movement at least three times that hereindicated would have been expected.

In addition the magnetic suspension of this invention has proved to beexceedingly immune to temporary or permanent magnetic change due toexternal magnetic fields to which it may be subjected either as a resultof intentional tampering or because of surge currents resulting fromlightning discharges striking the transmission lines. For example, withone prior commercial magnetic suspension of the repulsion type it hasbeen found that a readily available permanent magnet, when applied tothe external meter cover at the right place will so affect the magnetsof the magnetic suspension that they will allow the rotor to drop atleast 0.020 inch, or until the magnetic faces engage one another,thereby introducing great rotative friction. With the present invention,the same permanent magnet similarly applied will cause only a drop ofthe rotor of 0.004 inch, or less.

I claim:

1. A magnetic suspension for a rotor rotative about a vertical axis,said suspension including a pair of permanent magnets adapted for beingmounted respectively on the rotor and stationarily, the faces having thepolarity centers of the former facing generally downwardly and of thelatter facing generally upwardly; each having a surrounding annular poleface facing directly opposite the surrounding annular pole face of theother, and an inner pole face, with a circular outer boundary, facingand directly opposite the inner pole face of the other, said magnetsbeing similarly magnetized to repel each other, and being formed ofmaterial of high coercivity; in which the pole faces face axially andthe pole faces of each magnet are separated by an annular groove theradial width of which is not over approximately 3 mm, the face areas ofthe four poles being approximately equal.

2. A magnetic suspension for a rotor rotative about a vertical axis,said suspension including a pair of permanent magnets adapted for beingmounted respectively on the rotor and stationarily, the faces having thepolarity centers of the former facing generally downwardly and of thelatter facing generally upwardly; each having a surrounding annular polefacing facing directly opposite the surrounding annular pole face of theother, and an inner pole face, with a circular outer boundary, facingand directly opposite the inner pole face of the other, said magnetsbeing similarly magnetized to repel each other, and being formed ofmaterial of high coercivity; in which the pole faces face axially andthe pole faces of each magnet are separated by an annular groove theradial width of which is not over approximately 3 mm, the face areas ofthe four poles being approximately equal, the external diameter of saidmagnets being not over approximately inch.

3. A magnetic suspension fora rotor rotative about a vertical axis, saidsuspension including a pair of permanent magnets adapted for beingmounted respectively on the rotor and stationarily, the faces having thepolarity centers of the former facing generally downwardly and of thelatter facing generally upwardly; each having a surrounding annular poleface facing directly opposite the surrounding annular pole face of theother, and an inner pole face, with a circular outer boundary, facingand directly opposite the inner pole face of the other, said magnetsbeing similarly magnetized to repel each other, and being formed ofmaterial of high coercivity; in which the pole faces of each magnet areseparated by an annular groove the radial width of which is not overapproximately 3 mm.

4. A magnetic suspension for a rotor rotative about a vertical axis,said suspension including a pair of permanent magnets adapted for beingmounted respectively on the rotor and stationarily, the faces having thepolarity centers of the former facing generally downwardly and of thelatter facing generally upwardly; each having a surrounding annular poleface facing directly opposite the surrounding annular pole face of theother, and an inner pole face, with a circular outer boundary, facingand directly opposite the inner pole face of the other, said magnetsbeing similarly magnetized to repel each other, and being formed ofmaterial of high coercivity; in which the pole faces of each magnet areseparated by an annular groove the radial width of which is not overapproximately 3 mm, the external diameter of said magnets being not overapproximately inch.

5. A magnetic suspension for a rotor rotative about a vertical axis,said suspension including a pair of permanent magnets adapted for beingmounted respectively on the rotor and stationarily, the faces having thepolarity centers of the former facing generally downwardly and of thelatter facing generally upwardly; each having a surrounding annular poleface facing directly opposite the surrounding annular pole face of theother, and an inner pole face, with a circular outer boundary, facingand directly opposite the inner pole face of the other, said magnetsbeing similarly magnetized to repel each other, and being formed ofmaterial of high coercivity; in which the spacing between the pole facesof one magnet is at least as small as 3 mm.

6. A magnetic suspension for a rotor rotative about a vertical axis,said suspension including a pair of permanent magnets adapted for beingmounted respectively on the rotor and stationarily, the faces having thepolarity centers of the former facing generally downwardly and of thelatter facing generally upwardly; each having a surrounding annular poleface facing directly opposite the surrounding annular pole face of theother, and an inner pole face, with a circular outer boundary, facingand directly opposite the inner pole face of the other, said magnetsbeing similarly magnetized to repel each other, and being formed ofmaterial of high coercivity; in which the pole faces face axially andthe spacing between the inner and outer pole faces is at least as smallas 3 mm and the inner and outer pole faces have approximately the samearea.

7. A magnetic suspension for a rotor rotative about a vertical axis,said suspension including a pair of permanent magnets adapted for beingmounted respectively on the rotor and stationarily, the faces having thepolarity centers of the former facing generally downwardly and of thelatter facing generally upwardly; each having a surrounding annular poleface facing directly opposite the surrounding annular pole face of theother, and an inner pole face, with a circular outer boundary, facingand directly oppositethe inner pole face of the other, said magnetsbeing similarly magnetized to repel each other, and being formed ofmaterial of high coercivity; in which the spacing between the pole facesof one magnet is at least as small as 3 mm and in which none of saidpole faces is more than 40 percent larger in area than the smallest ofsaid pole faces.

8. A magnetic suspension for a rotor rotative about a vertical axis,said suspension including a pair of permanent magnets adapted for beingmounted respectively on the rotor and stationarily, the faces having thepolarity centers of the former facing generally downwardly and of thelatter facing generally upwardly; each having a surrounding annular poleface facing directly opposite the surrounding annular pole face of theother, and an inner pole face, with a circular outer boundary, facingand directly opposite the inner pole face of the other, said magnetsbeing similarly magnetizedto repel each other, and being'formed ofmaterial of high coercivity; in which the pole faces face axiallyand'the magnetic material is a material having a coercive force equal toat least 650 oersteds, in which the spacing between the pole faces is atleast as small as 3 mm, the pole face areas being approximately equal.

9. A magnetic suspension for a rotor rotative about a vertical axis,said suspension including a pair of permanent magnets each having asurrounding annular pole face axially facing directly opposite thesurrounding annular pole face of the other, and an inner pole face, witha circular outer boundary, axially facing and directly opposite theinner pole face of the other said pole faces all having polarity centersof the magnet poles therein said magnets being similarly magnetized torepel each other, and being formed of material of high coercivity, thefaces of each magnet being separated by a groove and the dimensions ofeach magnet in inches being approximately: outer diameter 0.5 6, radialdimensions of outer pole face 0.05, groove 0.04, inner pole face 0.11,said magnets being formed of Alnico VII powder molded with athermosetting synthetic plastic having a high temperature of heatdistortion, the magnets being in a stabilized partially demagnetizedstate in which the closest proximity of the magnets physically permittedwould not permanently demagnetize them further and in which they supportthe rotor with an axial gap between magnets of about 0.05 inch to 0.07inch, and having a temperature stability in which the gap betweenmagnets varies only about 0.003 inch with temperature changes fromminus'40 to plus 90C.

10. A magnetic suspension for a rotor rotative about a given axisincluding a pair of permanent magnets formed of high. coercive material,one carried by the rotor and the other fixed, each having an annularpole face surrounding said axis, directly opposite to and facing a likepole face of the other, and each having a second'pole face directlyopposite to and facing a like second pole face of the other, said polefaces all having polarity centers of the magnet poles therein said polesfaces being of approximately equal area, a groove in each'magnet assmall as 3 mm separating its pole faces; said magnets being similarlymagnetized for repulsion and being in a stabilized partiallydemagnetized state such as not to be further permanently demagnetized bythe closest proximity of the magnets physically permitted and at whichthe rotor is supported with a gap between the magnets at least of anorder of approximately the thickness of the groove.

11. A magnetic suspension for a rotor rotative about a given axisincluding a pair of permanent magnets formed of high coercive material,one carried by the rotor and the other fixed, each having an annularpole face surrounding said axis, directly opposite to and facing a likepole face of the other, and each having a second pole face directlyopposite to and facing a like second pole face of the other, said polefaces all having polarity centers of the magnet poles therein said polefaces being of approximately equal area, a groove in each magnet assmall as 3 mm separating its pole faces; said magnets being similarlymagnetized for repulsion.

12. A magnetic suspension for a rotor rotative about a vertical axis,said suspension including a pair of per manent magnets adapted for beingmounted respectively on the rotor and stationarily, the faces having thepolarity centers of the former facing generally downwardly and of thelatter facing generally upwardly; each having a surrounding annular poleface facing directly opposite the surrounding annular pole face of theother, and an inner pole face, with a circular outer boundary, facingand directly opposite the inner pole face of the other, said magnetsbeing similarly magnetized to repel each other and being formed ofmaterial of high coercivity; including a third permanent magnet ofcylindrical form concentric with said axis, said third magnet having agroove in its cylindrical surface dividing said surface into upper andlower outwardly facing cylindrical pole faces, a fourth permanentmagnet, surrounding said top and bottom poles and having an innercylindrical wall concentric with said axis, said fourth magnet having agroove in said wall in alignment with said groove in said surface anddividing said wall into upper and lower pole faces, directly facing theoutwardly facing pole faces; said third and fourth magnets being mountedrespectively with said first named magnets, and being magnetized withthe top poles of one polarity and the bottom poles of the oppositepolarity for mutual repulsion to concentricity.

13. A magnetic suspension for a rotor rotative about a vertical axis,said suspension including a pair of permanent magnets adapted for beingmounted respectively on the rotor and stationarily, the faces having thepolarity centers of the former facing generally downwardly and of thelatter facing generally upwardly; each having a surrounding annular poleface facing directly opposite the surrounding annular pole face of theother, and an inner pole face, with a circular outer boundary, facingand directly opposite the inner pole face of the other, said magnetsbeing similarly magnetized to repel each other, and being formed ofmaterial of high coercivity; in which a pair of magnets, one adapted formounting on the rotor and the other for mounting stationarily, eachhastwo poles directly facing the two poles of the other somewhat radially,each magnet of said suspension having the spacing between its pole facesat least as small as 3 mm.

14. In a permanent magnet bearing having a pair of spaced bearingmembers with closely spaced facing surfaces defining a separating airgap, one of said members being rotatable with respect to the other ofsaid members on an axis generally perpendicular to said surfaces, theimprovement comprising: each of said members having substantiallyidentical pairs of opposite polarity, circular magnetic poles on saidfacing surfaces and coaxial with said axis with the poles of one memberfacing like poles on the other member and the axes of magnetization ofeach of said poles being substantially normal to said facing surfacesand extending through said air gap whereby the lines of force of saidpoles are concentrated within said air gap; said oppositepolarityconcentric poles on each of said surfaces having substantially equalpole areas.

15. In a permanent magnet bearing having a pair of spaced bearingmembers with closely spaced facing surfaces defining a separating airgap, one of said members being rotatable with respect to the other ofsaid members on an axis generally perpendicular to said surfaces, theimprovement comprising: each of said members having substantiallyidentical pairs of opposite polarity, circular magnetic poles on saidfacing surfaces and coaxial with said axis with the poles of one memberconcentrated within said air gap; said members comprising a permanentmagnetic material having a coercive force at least that of Alnico VII.

g UNITEE STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,807,813 Dated *Apr. 30, 1974 'Inventofls) James W. Milligan It iscertified that error appears in the above-identified patent and thatsaid Letters Patentare hereby corrected as shown below:

Column 2', line 9, "construction; should be constructions; I

Column 2, lines 59,- 60, "rotation" should be rotating Column 3', line29, after "binding metal", "29' should be 29' v 1 Column 3, line 30,"magent" should be magnet- 7 Column 3, line 31, after "collar", "29"should be -29 Column 3, line 48, "although" should be Although Column 4,line 31, "fixture of" should be i fixture for Column 5, line 33, before"stabilization", "is" should be if Column 6, line 9, before "passed","not" should be now Column 6, line 27, before "41 and 42" insert facesColumn 9, line 22, "has" should be had Column ll, line 33, "pole facingfacing" should read pole face facing Column 13, "line 14, insert commaafter "other". I Column .13, line l8, after "coercivity", change commato semicolon,

Column l3, line 43, "said poles" should read --said pole Signed andsealed this 22nd day of October .1974.

(SEAL) Attest:

Mendy M. GIBSON JR. c.. MARSHALL DANN Arresting Officer Commissioner ofPatents ORM Po-1o50 (10-69) y t, USCOMM-DC 60376-P89 i [1.5. GOVIRNHINTPQINTING PFFICE; 19. 0-355-334.

UNnEu STATES PA"ENT OFFICE (JERTlFlCATE OF CORRECTION Patent No.3,807,813 Dated Apr. 30, 1974 Inventor(s Jarnes W. Milligan It iscertified that error appears in the above-identified patent and thatsaid Letters Patentere hereby corrected as shown below:

Column 2, line 9, "construction; should be constructions;

Column 2,, lines 59,- 60, "rotation" should be rotating Column 3, line29, after "binding metal", "29' should be 29 Column 3, line 30, "magent"should be -'*'-magnet- Column 3, line 31, after "collar", "29" should be----29 Column 3, line 48, "although" should be Although Column 4, line31, "fixture of" should be fixture for Column 5, line 33, before"stabilization", "is" should be if Column 6, line 9, I before "passed","not" should be now Column 6, line 27, before "41 and 42" insert facesColumn 9, line 22, "has" should be had Column ll, line 33, "pole facingfacing" should read pole face facing Column l3, vline l4, insert commaafter "other". I Column 13, line 18, after "coercivity", change comma tosemicolon,

Column 13, line 43, "said poles" should read --said pole Signed andsealed this 22nd day of October .197

(SEAL) Attest:

moor GIBSON JR. c.. MARSHALL DANN v Arresting Officer Commissioner ofPatents ORM PC4050 (10-69) v -gc 0375-p59 ".5. GOVIRIMINT 'IINTINGOFFICE 19'! O-3ii-33L

1. A magnetic suspension for a rotor rotative about a vertical axis,said suspension including a pair of permanent magnets adapted for beingmounted respectively on the rotor and stationarily, the faces having thepolarity centers of the former facing generally downwardly and of thelatter facing generally upwardly; each having a surrounding annular poleface facing directly opposite the surrounding annular pole face of theother, and an inner pole face, with a circular outer boundary, facingand directly opposite the inner pole face of the other, said magnetsbeing similarly magnetized to repel each other, and being formed ofmaterial of high coercivity; in which the pole faces face axially andthe pole faces of each magnet are separated by an annular groove theradial width of which is not over approximately 3 mm, the face areas ofthe four poles being approximately equal.
 2. A magnetic suspension for arotor rotative about a vertical axis, said suspension including a pairof permanent magnets adapted for being mounted respectively on the rotorand stationarily, the faces having the polarity centers of the formerfacing generally downwardly and of the latter facing generAlly upwardly;each having a surrounding annular pole facing facing directly oppositethe surrounding annular pole face of the other, and an inner pole face,with a circular outer boundary, facing and directly opposite the innerpole face of the other, said magnets being similarly magnetized to repeleach other, and being formed of material of high coercivity; in whichthe pole faces face axially and the pole faces of each magnet areseparated by an annular groove the radial width of which is not overapproximately 3 mm, the face areas of the four poles being approximatelyequal, the external diameter of said magnets being not overapproximately 3/4 inch.
 3. A magnetic suspension for a rotor rotativeabout a vertical axis, said suspension including a pair of permanentmagnets adapted for being mounted respectively on the rotor andstationarily, the faces having the polarity centers of the former facinggenerally downwardly and of the latter facing generally upwardly; eachhaving a surrounding annular pole face facing directly opposite thesurrounding annular pole face of the other, and an inner pole face, witha circular outer boundary, facing and directly opposite the inner poleface of the other, said magnets being similarly magnetized to repel eachother, and being formed of material of high coercivity; in which thepole faces of each magnet are separated by an annular groove the radialwidth of which is not over approximately 3 mm.
 4. A magnetic suspensionfor a rotor rotative about a vertical axis, said suspension including apair of permanent magnets adapted for being mounted respectively on therotor and stationarily, the faces having the polarity centers of theformer facing generally downwardly and of the latter facing generallyupwardly; each having a surrounding annular pole face facing directlyopposite the surrounding annular pole face of the other, and an innerpole face, with a circular outer boundary, facing and directly oppositethe inner pole face of the other, said magnets being similarlymagnetized to repel each other, and being formed of material of highcoercivity; in which the pole faces of each magnet are separated by anannular groove the radial width of which is not over approximately 3 mm,the external diameter of said magnets being not over approximately 3/4inch.
 5. A magnetic suspension for a rotor rotative about a verticalaxis, said suspension including a pair of permanent magnets adapted forbeing mounted respectively on the rotor and stationarily, the faceshaving the polarity centers of the former facing generally downwardlyand of the latter facing generally upwardly; each having a surroundingannular pole face facing directly opposite the surrounding annular poleface of the other, and an inner pole face, with a circular outerboundary, facing and directly opposite the inner pole face of the other,said magnets being similarly magnetized to repel each other, and beingformed of material of high coercivity; in which the spacing between thepole faces of one magnet is at least as small as 3 mm.
 6. A magneticsuspension for a rotor rotative about a vertical axis, said suspensionincluding a pair of permanent magnets adapted for being mountedrespectively on the rotor and stationarily, the faces having thepolarity centers of the former facing generally downwardly and of thelatter facing generally upwardly; each having a surrounding annular poleface facing directly opposite the surrounding annular pole face of theother, and an inner pole face, with a circular outer boundary, facingand directly opposite the inner pole face of the other, said magnetsbeing similarly magnetized to repel each other, and being formed ofmaterial of high coercivity; in which the pole faces face axially andthe spacing between the inner and outer pole faces is at least as smallas 3 mm and the inner and outer pole faces have approximately the samearea.
 7. A magnetic suspension for a rotor rotative about a verticalaxis, saId suspension including a pair of permanent magnets adapted forbeing mounted respectively on the rotor and stationarily, the faceshaving the polarity centers of the former facing generally downwardlyand of the latter facing generally upwardly; each having a surroundingannular pole face facing directly opposite the surrounding annular poleface of the other, and an inner pole face, with a circular outerboundary, facing and directly opposite the inner pole face of the other,said magnets being similarly magnetized to repel each other, and beingformed of material of high coercivity; in which the spacing between thepole faces of one magnet is at least as small as 3 mm and in which noneof said pole faces is more than 40 percent larger in area than thesmallest of said pole faces.
 8. A magnetic suspension for a rotorrotative about a vertical axis, said suspension including a pair ofpermanent magnets adapted for being mounted respectively on the rotorand stationarily, the faces having the polarity centers of the formerfacing generally downwardly and of the latter facing generally upwardly;each having a surrounding annular pole face facing directly opposite thesurrounding annular pole face of the other, and an inner pole face, witha circular outer boundary, facing and directly opposite the inner poleface of the other, said magnets being similarly magnetized to repel eachother, and being formed of material of high coercivity; in which thepole faces face axially and the magnetic material is a material having acoercive force equal to at least 650 oersteds, in which the spacingbetween the pole faces is at least as small as 3 mm, the pole face areasbeing approximately equal.
 9. A magnetic suspension for a rotor rotativeabout a vertical axis, said suspension including a pair of permanentmagnets each having a surrounding annular pole face axially facingdirectly opposite the surrounding annular pole face of the other, and aninner pole face, with a circular outer boundary, axially facing anddirectly opposite the inner pole face of the other said pole faces allhaving polarity centers of the magnet poles therein said magnets beingsimilarly magnetized to repel each other, and being formed of materialof high coercivity, the faces of each magnet being separated by a grooveand the dimensions of each magnet in inches being approximately: outerdiameter 0.56, radial dimensions of outer pole face 0.05, groove 0.04,inner pole face 0.11, said magnets being formed of Alnico VII powdermolded with a thermosetting synthetic plastic having a high temperatureof heat distortion, the magnets being in a stabilized partiallydemagnetized state in which the closest proximity of the magnetsphysically permitted would not permanently demagnetize them further andin which they support the rotor with an axial gap between magnets ofabout 0.05 inch to 0.07 inch, and having a temperature stability inwhich the gap between magnets varies only about 0.003 inch withtemperature changes from minus 40* to plus 90*C.
 10. A magneticsuspension for a rotor rotative about a given axis including a pair ofpermanent magnets formed of high coercive material, one carried by therotor and the other fixed, each having an annular pole face surroundingsaid axis, directly opposite to and facing a like pole face of theother, and each having a second pole face directly opposite to andfacing a like second pole face of the other, said pole faces all havingpolarity centers of the magnet poles therein said poles faces being ofapproximately equal area, a groove in each magnet as small as 3 mmseparating its pole faces; said magnets being similarly magnetized forrepulsion and being in a stabilized partially demagnetized state such asnot to be further permanently demagnetized by the closest proximity ofthe magnets physically permitted and at which the rotor is supportedwith a gap between the magnets at least of an order of approximately thethickness of the groove.
 11. A magnetic suspension for a rotor rotativeabout a given axis including a pair of permanent magnets formed of highcoercive material, one carried by the rotor and the other fixed, eachhaving an annular pole face surrounding said axis, directly opposite toand facing a like pole face of the other, and each having a second poleface directly opposite to and facing a like second pole face of theother, said pole faces all having polarity centers of the magnet polestherein said pole faces being of approximately equal area, a groove ineach magnet as small as 3 mm separating its pole faces; said magnetsbeing similarly magnetized for repulsion.
 12. A magnetic suspension fora rotor rotative about a vertical axis, said suspension including a pairof permanent magnets adapted for being mounted respectively on the rotorand stationarily, the faces having the polarity centers of the formerfacing generally downwardly and of the latter facing generally upwardly;each having a surrounding annular pole face facing directly opposite thesurrounding annular pole face of the other, and an inner pole face, witha circular outer boundary, facing and directly opposite the inner poleface of the other, said magnets being similarly magnetized to repel eachother and being formed of material of high coercivity; including a thirdpermanent magnet of cylindrical form concentric with said axis, saidthird magnet having a groove in its cylindrical surface dividing saidsurface into upper and lower outwardly facing cylindrical pole faces, afourth permanent magnet, surrounding said top and bottom poles andhaving an inner cylindrical wall concentric with said axis, said fourthmagnet having a groove in said wall in alignment with said groove insaid surface and dividing said wall into upper and lower pole faces,directly facing the outwardly facing pole faces; said third and fourthmagnets being mounted respectively with said first named magnets, andbeing magnetized with the top poles of one polarity and the bottom polesof the opposite polarity for mutual repulsion to concentricity.
 13. Amagnetic suspension for a rotor rotative about a vertical axis, saidsuspension including a pair of permanent magnets adapted for beingmounted respectively on the rotor and stationarily, the faces having thepolarity centers of the former facing generally downwardly and of thelatter facing generally upwardly; each having a surrounding annular poleface facing directly opposite the surrounding annular pole face of theother, and an inner pole face, with a circular outer boundary, facingand directly opposite the inner pole face of the other, said magnetsbeing similarly magnetized to repel each other, and being formed ofmaterial of high coercivity; in which a pair of magnets, one adapted formounting on the rotor and the other for mounting stationarily, each hastwo poles directly facing the two poles of the other somewhat radially,each magnet of said suspension having the spacing between its pole facesat least as small as 3 mm.
 14. In a permanent magnet bearing having apair of spaced bearing members with closely spaced facing surfacesdefining a separating air gap, one of said members being rotatable withrespect to the other of said members on an axis generally perpendicularto said surfaces, the improvement comprising: each of said membershaving substantially identical pairs of opposite polarity, circularmagnetic poles on said facing surfaces and coaxial with said axis withthe poles of one member facing like poles on the other member and theaxes of magnetization of each of said poles being substantially normalto said facing surfaces and extending through said air gap whereby thelines of force of said poles are concentrated within said air gap; saidopposite polarity concentric poles on each of said surfaces havingsubstantially equal pole areas.
 15. In a permanent magnet bearing havinga pair of spaced bearing members with closely spaced facing surfacesdefining a separating air gap, one of said members being rotatable withrespect to the other of said members on an axis generally perpendicularto said surfaces, the improvement comprising: each of said membershaving substantially identical pairs of opposite polarity, circularmagnetic poles on said facing surfaces and coaxial with said axis withthe poles of one member facing like poles on the other member and theaxes of magnetization of each of said poles being substantially normalto said facing surfaces and extending through said air gap whereby thelines of force of said poles are concentrated within said air gap; saidmembers comprising a permanent magnetic material having a coercive forceat least that of Alnico VII.